Arrangement for disconnecting consumers from a direct current voltage supply source

ABSTRACT

A protective circuit arrangement is provided for disconnecting a consumer requiring different potentials at different input terminals from a direct current power source having two output terminals supplying the different potentials in the event of a short-circuit between the potential terminals. The protective circuit includes a pair of mechanical circuit breakers located respectively in the connection lines extending between the power output and consumer input terminals which are each equipped with current overload contact release mechanisms and an electronic circuit responsive upon the occurrence of a short-circuit between the potential terminals serves to establish a current flow path from one of the connection lines to ground and short-circuit the input terminals of the consumer until one of the circuit breakers functions through its current overload release mechanism to open its contacts. The contacts of the two circuit breakers are mechanically coupled by an insulating coupling so that an opening movement of the contacts of one circuit breaker causes the contacts of the other circuit breaker to open also.

United States Patent Lau et aL, Sept. 5, 1972 54 ARRANGEMENT FOR 3,571,659 3/1971 Anzal ..317/16 DISCONNECTING CONSUMERS FROM 3,573,554 4/1971 Theobald ..317/46 A DIRECT CURRENT VOLTAGE SU SOURCE Primary ExaminerJ. D. Miller Assistant ExaminerHarvey Fendelman [72] Inventors. Waldemar Lau, l-lockenheim; Anton Attorney pierce, S h m & Parker Schaffernak, Eppelheim, both of Germany [57] ABSTRACT Assignee! Mitillllgeseusiiha- Boveri & A protective circuit arrangement is provided for Baden, SWllZerland disconnecting a consumer requiring different poten- [22] Filed: April 20 1971 tials at different input terminals from a direct current 9 power source having two output terminals supplying PP No.2 135,665 the different potentials in the event of a short-circuit between the potential terminals. The protective circuit 3 includes a pair of mechanical circuit breakers located 0] Forelgn Apphcauon Pnomy Data respectively in the connection lines extending between April 30, 1970 Germany ..P 20 21 206.0 the power output and consumer input terminals which 1 I are each equipped with current overload contact [52] US. Cl. ..317/16, 317/31, 317/27, release m anisms and an electronic circuit respon- 317/33 SC, 307/86 317/46, 307/94 307/130 sive upon the occurrence of a short-circuit between 51 Int. Cl. ..H02h 3/20. the Potential terminals Serves to establish a current [58] Field of Search .;'...317/46, 16, 31, 27, 33 so; l P from one of h connection lines to ground 07 94 100, 131, 130, 86 and short-circuit the input terminals of the consumer until one of the circuit breakers functions through its 5 References Cited current overload release mechanism to open its contacts. The contacts of the two circuit breakers are UNITED STATES PATENTS mechanically coupled by an insulating coupling so that an opening movement of the contacts of one circuit breaker causes the contacts of the other circuit aco S breaker to Open 8180 3,225,257 12/1965 Fegley ..317/46 X 3.475.653 10/ 1969 Odenberg ..317/16 6 Claims, 2 Drawing Figures 2 5 1a 5 jLe I A 7a.

N 8 60. 4. d I 3 5 ARRANGEMENT FOR DISCONNECTING CONSUMERS FROM A DIRECT CURRENT VOLTAGE SUPPLY SOURCE This invention relates to an improved arrangement for effecting the separation of a consumer from a direct current power source provided with two different output potentials whenever a short-circuit appears between the potential terminals that are each connected to the consumer.

Consumer systems of the electronic type often require, for their d.c. voltage supplys, d.c. voltages of different magnitude and polarity. The difference between the required d.c. voltages may amount to as much as 200 volts in the case where semiconductor components for numeral indicator tubes are used at the same time. Since it is advantageous for reasons of space utilization to draw all d.c. voltages required, from a single power supply arrangement, safety measures must be taken to protect the extremely sensitive semiconductor components of the possibly already connected electronic system against excess voltages in the event of short-circuits between the various voltage terminals of the power supply arrangement. Such protective arrangements should have as short a response time as possible since even brief, high voltage pluses may lead to either the damage," or complete destruction of the semiconductorcomponents. Another requirement to be met by such protective devices is their re-usability after having been triggered, whereby safe operation, even after frequent triggering, must be assured.

A number of different protective devices are known but all of these have the disadvantage, however, that either the response time is too long, or that they are destroyed after triggering and must be replaced. In US. Pat. No. 3,163,814, a fully electronic protective device is disclosed which avoids these disadvantages but the device is very expensive.

The principal objective of the present invention is to provide an improved protective device of the character described which is relatively simple and inexpensive and also avoids the two disadvantages referred to above. That is to say, the protective device has a satisfactorily short response time and can be re-used repeatedly.

In accordance with the invention, the problem is solved in that a mechanical circuit breaker is disposed between each of the different voltage output terminals of the d.c. voltage supply source and the corresponding input terminals of the consumer, and that in the event of a short-circuit between the output terminals of the d.c. power source, or between the input terminals of the consumer, an electronic circuit is activated to provide a connection between the wire carrying the lower of the two d.c. output voltages and a ground wire which thereby serves to connect both input terminals of the consumer to ground potential until the circuit breaker responds and isolates the consumer input terminals from its d.c. power supply source.

In accordance with one suitable preferred embodiment of the invention, the electronic circuit connector to establish the desired short-circuit is formed by an inseries arrangement of a Zener diode connected to the connecting wire with the lowest d.c. potential and of a blocking resistor, as well as by a thyristor paralleled to this in-series arrangement of the Zener diode and blocking resistor. In the event of a short-circuit between the two different d.c. voltage terminals of the power supply,the control electrode of the thyristor is charged with a current pulse flowing through the Zener diode which serves to ignite the thyristor. It is also advantageous for a current limiting resistor to be connected between the connecting wire having the lowest d.c. potential and the thyristor.

In accordance with another suitable embodiment of the invention, the solution to the problem 'is characterized in that a mechanical circuit breaker is disposed between each of the different voltage output terminals of the d.c. voltage supply source and the corresponding input terminals of the consumer, that an inseries arrangement of a Zener diode and blocking resistor is disposed between a connecting wire having the lowest d.c. supply potential and a ground wire, and that a thyristor is disposed between a connecting wire having the highest d.c. supply potential and the ground wire. In a preferred implementation of this second solution to the problem a current limiting resistor is also provided between the connecting wire having the highest d.c. supply potential and the ground wire, this resistor being connected in series with the thyristor.

In both of the embodiments of the invention which have been referred to, it it expedient mechanically couplethe switching contacts of the two circuit breakers to each other by means of an electrically insulating interconnecting element so that when one of the circuit breakers is tripped to its open position, the switch contacts of the other circuit breaker are also pulled open due to this mechanical interconnection between the circuit breakers.

The principal advantages achieved by the invention are the use of relatively few components which assure, at little cost, reusability many times with optimal functional reliability.

The invention will now be described in greater detail as applied to the aforementioned embodiments and in conjunction with the accompanying drawings wherein:

FIG. 1 is a schematic electrical circuit diagram of a dual d.c. voltage supply circuit together with one embodiment of the inventive consumer protective circuit; and

FIG. 2 is also a schematic electrical circuit diagram similar to that of FIG. 1 but illustrating a modification for the arrangement of the current limiting resistor that is connected in series with the thyristor element of the protective circuit.

With reference now to the drawings, in each embodiment, 1 and 2 designate the voltage output terminals of a d.c. power supply source 3 which have different potential levels; 4 and 5 are input terminals of a not further detailed consumer; 6 are mechanical circuit breakers; 7 switch contacts; 8 is a coupling element; 9 a voltage-carrying connecting wire; 10 a ground wire; 11 an electronic circuit connector; 12 a Zener diode; 13 a blocking resistor; 14 a thyristor; 15 a limiting resistor; 16 and 17 are impedances of the d.c. power source 3; and 18 is another voltage-carrying connecting wire.

As is evident from FIG. 1, mechanical circuit breakers 6 are provided respectively between each of the output terminals 1, 2 of a d.c. power source 3 and input terminals 4, 5 of a not further detailed consumer of the electronic type including semiconductor com ponents requiring protection. The switch contacts 7 of the circuit breakers 6 are mechanically interconnected with each other through an electrically insulating, rigid coupling element 8. An electronic circuit connector 1 1 is disposed between a connecting wire 9 having the lowest of the two d.c. output potentials and a ground wire 10. In the event of a short-circuit between the output terminals 1, 2 of the d.c. power source 3, or between the input terminals 4, 5 of the consumer, the electronic circuit connector 11 responds and establishes a current-carrying connection between the connecting wire 9 and the ground wire 10. The input terminals 4, 5 of .the consumer are thereby connected to ground potential so that the excess voltage prevailing at the input terminal 5, up to the response of the electronic circuit connector 11, collapses. The response time of the circuit connector 11 amounts to a few microseconds and is thus below the limital duration of a voltage pulse harmful to the semiconductor components of the consumer. The circuit connector 11 maintainsthe current-carrying connection between the connecting wire 9 and the ground wire 10 until a sufficiently strong magnetic field has built up in the coil of one of the circuit breakers 6, due to the short-circuit current, to break the switch contact 7. As a resultof the mechanical coupling of the switch contacts 7 of both circuit breakers, breaking of the switch contacts of one circuit breaker causes the switch contacts of the other circuit breaker to break at the same time so that the consumer is disconnected completely from the dual voltage d.c. power source 3. The response time of the circuit breaker 6 is longer by a factor of 10 than the response time of the circuit connector 11 and hence would, by itself be too long to protect the semiconductor components of the consumer effectively. On the other hand, the time span between the response of the circuit connector 11 and the tripping of the circuit breaker 6 is too short for the electronic circuit connector 11 to become damaged or destroyed by the partly very high short-circuit current pulse, thereby assuring the reusability of the entire protective device.

In detail, the electronic circuit connector 11 consists of two parallel branches of which one branch is formed by the inseries arrangement of a Zener diode l2 and a blocking resistor 13 and the other branch of a thyristor 14. For current limitation, a limiting resistor may be inserted between the anode of the thyristor 14 and the lower voltage-carrying connecting wire 9. The cathode of Zener diode 12 is connected to the lowest voltage so that this diode blocks in the normal operating condition, the threshold voltage dropping at it. The anode of the Zener diode 12 is connected to one end of the blocking resistor 13, on the one hand, and to the control electrode of the thyristor 14 on the other hand. If, in the event of a short-circuit, the voltage at the branch 12/13 exceeds the threshold voltage of the Zener diode 12, this diode becomes currentcarrying. By suitably dimensioning the blocking resistor 13, the control electrode of the thyristor 14 is charged with the current pulse flowing through the diode 12 so that the thyristor 14 ignites. The resistance of the branch 14/15 thereby becomes considerably smaller than the resistance of branch 12/13; this means that the conduction of current through diode 12 ceases, and the entire short-circuit current flows through the limiting resistor 15 and the thyristor 14. This process continues until the circuit breaker 6 trips, disconnecting the d.c. power source 3. The current overload trip coil for circuit breaker 6 is indicated schematically at 6a, and the overload trip coil for circuit breaker 7 is likewise illustrated at 70.

At certain relative sizes of the impedances 16,17 of the d.c. power source 3 it may be expedient (FIG. 2) to connect the limiting resistor 15 to the connecting wire 18 having the higher d.c. potential. The operating mode of the circuit connector 11 is the same as that of the circuit connector 11 according to FIG. 1 because there is a conductive connection between the connecting wires 9 and 18 in the event of a short-circuit.

We claim:

1. A protective circuit arrangement for disconnecting a consumer requiring different potentials at different input terminals thereof from a direct current power source having two output terminals supplying the different potentials in the event of a short-circuit between the potential terminals, which comprises a pair of mechanical circuit breakers located respectively in the connection lines extending between said power output and consumer input terminals a current overload release mechanism provided on each circuit breaker for opening the breaker'contacts, and an electronic circuit means responsive upon the occurrence of a short-circuit between the potential terminals for establishing a current flow path between said connection line having the lower of said potentials and ground thereby to short-circuit said input terminals until one of said circuit breakers functions through its current overload release mechanism to open its contacts, said elec tronic circuit means being constituted by a Zener diode connected in series with a blocking resistor and a thyristor connected in parallel with said series connected Zener diode and blocking resistor, the ignition electrode of said thyristor being connected to the junction between said Zener diode and blocking resistor.

2. A protective circuit arrangement as defined in claim 1 and which further includes means establishing an insulating mechanical coupling between the contacts of both circuit breakers such that when the contacts of one breaker are opened in response to operation of its current overload release, the contacts of the other circuit breaker are also opened.

3. A protective arrangement as defined in claim 1 and which further includes a limiting resistor interposed between the connection line having the lower of said potentials and said thyristor.

4. A protective arrangement operative for disconnecting a consumer requiring different potentials at different input terminals thereof from a direct current power source having two output potentials supplying the different potentials in the event of a short-circuit between the potential terminals, which comprises a pair of mechanical circuit breakers located respectively in the connection lines extending between said power output and consumer input terminals, a current overload release provided on each circuit breaker for opening the breaker contacts, a Zener diode and a blocking resistor connected in series between said connection line having the lower of said potentials and ground, and a thyristor connected between said connection line having thehigher of said potentials and ground, the ignition electrode of said thyristor being connected to the junction between said Zener diode and blocking re- 6. A protective arrangement as defined in claim 4 and which further includes means establishing an insulating mechanical coupling between the contacts of both circuit breakers such that when the contacts of one circuit breaker are opened in response to operation of its current overload release, the contacts of the other circuit breaker are opened. 

1. A protective circuit arrangement for disconnecting a consumer requiring different potentials at different input terminals thereof from a direct current power source having two output terminals supplying the different potentials in the event of a short-circuit between the potential terminals, which comprises a pair of mechanical circuit breakers located respectively in the connection lines extending between said power output and consumer input terminals a current overload release mechanism provided on each circuit breaker for opening the breaker contacts, and an electronic circuit means responsive upon the occurrence of a short-circuit between the potential terminals for establishing a current flow path between said connection line having the lower of said potentials and ground thereby to short-circuit said input terminals until one of said circuit breakers functions through its current overload release mechanism to open its contacts, said electronic circuit means being constituted by a Zener diode connected in series with a blocking resistor and a thyristor connected in parallel with said series connected Zener diode and blocking resistor, the ignition electrode of said thyristor being connected to the junction between said Zener diode and blocking resistor.
 2. A protective circuit arrangement as defined in claim 1 and which further includes means establishing an insulating mechanical coupling between the contacts of both circuit breakers such that when the contacts of one breaker are opened in response to operation of its current overload release, the contacts of the other circuit breaker are also opened.
 3. A protective arrangement as defined in claim 1 and which further includes a limiting resistor interposed between the connection line having the lower of said potentials and said thyristor.
 4. A protective arrangement operative for disconnecting a consumer requiring different potentials at different input terminals thereof from a direct current power source having two output potentials supplying the different potentials in the event of a short-circuit between the potential terminals, which comprises a pair of mechanical circuit breakers located respectively in the connection lines extending between said power output and consumer input terminals, a current overload release provided on each circuit breaker for opening the breaker contacts, a Zener diode and a blocking resistor connected in series between said connection line having the lower of said potentials and ground, and a thyristor connected between said connection line having the higher of said potentials and ground, the ignition electrode of said thyristor being connected to the junction between said Zener diode and blocking resistor and said thyristor being ignited in the event of a short-circuit between said potential terminals to short-circuit said input terminals until one of said circuit breakers functions through its current overload release to open its contacts.
 5. A protective arrangement as defined in claim 4, and which further includes a limiting resistor interposed between the connection line having the higher of said potentials and said thyristor.
 6. A protective arrangement as defined in claim 4 and which further includes meaNs establishing an insulating mechanical coupling between the contacts of both circuit breakers such that when the contacts of one circuit breaker are opened in response to operation of its current overload release, the contacts of the other circuit breaker are opened. 